Atmosphere
Space life support systems maintain atmospheres composed, at a minimum, of oxygen, water vapor and carbon dioxide. The partial pressure of each component gas adds to the overall barometric pressure.
By reducing or omitting diluents (constituents other than oxygen, e.g., nitrogen and argon) the total pressure can be lowered to a minimum of 21 kPa, the partial pressure of oxygen in the Earth's atmosphere at sea level. This can lighten spacecraft structures, reduce leaks and simplify the life support system.
However, the elimination of diluent gases substantially increases fire risks, especially in ground operations when for structural reasons the total cabin pressure must exceed the external atmospheric pressure; see Apollo 1. For this reason, most modern crewed spacecraft use conventional air (nitrogen/oxygen) atmospheres and use pure oxygen only in pressure suits during extravehicular activity where acceptable suit flexibility mandates the lowest inflation pressure possible.
Read more about this topic: Life Support System
Famous quotes containing the word atmosphere:
“It is better to have your head in the clouds, and know where you are ... than to breathe the clearer atmosphere below them, and think that you are in paradise.”
—Henry David Thoreau (1817–1862)
“The atmosphere parents wish to create when talking with children about birth and reproduction is warm, honest, and reassuring, one that tells children they are free to ask questions as often as they need to, and you will answer them as lovingly as you know how.”
—Joanna Cole (20th century)
“The man who, from the beginning of his life, has been bathed at length in the soft atmosphere of a woman, in the smell of her hands, of her bosom, of her knees, of her hair, of her supple and floating clothes, ... has contracted from this contact a tender skin and a distinct accent, a kind of androgyny without which the harshest and most masculine genius remains, as far as perfection in art is concerned, an incomplete being.”
—Charles Baudelaire (1821–1867)